Recently, with the expected exhaustion of the existing energy resources such as petroleum or coal, there is a growing interest in energy which may substitute for the existing energy resources. As one of these alternative energies, a fuel cell is receiving particular attention due to the advantages in that the fuel cell is highly efficient and does not discharge pollutants such as NOx and SOx, and the fuel used is abundant.
A fuel cell is a power generation system which converts chemical reaction energy of a fuel and an oxidizing agent into electric energy, and representatively, hydrogen and hydrocarbons such as methanol or butane are used as the fuel, and oxygen is used as the oxidizing agent.
Examples of the fuel cell include a polymer electrolyte membrane fuel cell (PEMFC), a direct-methanol fuel cell (DMFC), a phosphoric acid fuel cell (PAFC), an alkaline fuel cell (AFC), a molten carbonate fuel cell (MCFC), a solid oxide fuel cell (SOFC), and the like.
Meanwhile, there is also a need for studying a metal-air secondary battery in which a cathode of a metal secondary battery is manufactured as an air electrode by applying a principle of an air electrode of a fuel cell.